The present invention relates to a radioactive waste treatment facility for solidification of radioactive waste, which is generated from radioactive material handling facilities such as nuclear power plants, fuel reprocessing plants, and the like.
The radioactive waste generated from radioactive material handling facilities such as nuclear power plants, fuel reprocessing plants, and the like is generally solidified with a hydraulic solidifying material such as cement and the like. In accordance with the above processing, not only the volume of the radioactive waste can be reduced, but also stable a solidified waste superior in long term duration can be obtained.
Generally, the radioactive waste is classified to various groups having different properties each other such as miscellaneous solid waste, concentrated liquid waste, spent resin, ashes, and others. Respective of the groups is handled with an appropriate treating method of injecting solidification or kneading solidification depending on its kind and properties.
The injecting solidification is a method, in which the waste is contained in a drum first, and then, a solidifying agent is injected into the drum from the top of the drum for solidification. The injecting solidification method is applied to incombustible miscellaneous solid waste such as pipes and others, with which the solidifying agent can be flowed down through intervals among the solid waste.
The kneading solidification is a method, in which the waste is solidified by kneading with a solidifying agent. The kneading solidification method is applied to powder, granular, or liquid waste such as concentrated liquid waste and its dried powder, spent resin, ashes, and the like. At this time, there are in-drum type and out-drum type for the kneading method. The in-drum type method is a method, in which, after charging the waste and a solidifying agent together into a solidifying container (or during charging), a kneading blade is inserted into the charged materials to knead them. The out-drum type method is a method, in which, after charging the waste and a solidifying agent together into an exclusive kneading container and kneading the charged materials by inserting a kneading blade therein, the kneaded material is poured into a solidifying container.
As explained above, the injecting solidification and the kneading solidification are different solidification methods each other. Therefore, in order to treat miscellaneous many kind radioactive wastes adequately, an appropriate solidification facility must be provided respectively, and a significantly broad installation site area was required.
In order to solve the above problem, a radioactive waste treatment facility (solidification facility) comprising; a transferring means for transferring solidifying containers; an out-drum mixer type kneader which is capable of preparing kneaded material by charging a solidifying agent, additive water, and the radioactive waste together therein and kneading them; and a kneaded material injecting means, which injects the kneaded material into a solidifying container at a designated location in the transferring direction of the transferring means; is disclosed in JP-A-8-29594 (1996).
In accordance with the radioactive waste treatment facility, when performing the injection and solidification of the radioactive miscellaneous solid waste and others, a solidifying container wherein the radioactive waste is supplied previously is transferred to a designated location by the transferring means; only the solidifying agent and the additive water are charged into the kneader to prepare a solidifying agent paste; and the solidifying agent paste is injected into the solidifying container by the kneaded material injecting means. Accordingly, the solidifying agent paste is flowed down through the intervals among the solid waste to be filled into the solidifying container, and a solidified waste as same as the one obtained by a normal injecting solidification method can be prepared.
On the other hand, when concentrated liquid waste, spent resin, ashes, and the like are solidified by the kneading solidification, a solidified waste (homogeneous solidified waste), wherein the solidifying paste and the radioactive waste are mixed thoroughly, as same as the one obtained by a normal injecting solidification method can be prepare by the steps of: transferring an empty solidifying container to a designated location by the transferring means; charging a solidifying agent, additive water, and the radioactive waste into a kneading vessel of the kneader; agitating the charged material with kneading blade to form a kneaded material; and injecting the kneaded material into the solidifying container by the kneaded material injecting means.
In accordance with the prior art described above, kneading the solidifying paste (solidifying agent+additive water) for kneading solidification, and kneading the kneaded material for kneading solidification are performed by a similar out-drum-mixer type kneader, in order to make it possible to perform injecting solidification and kneading solidification together by a single facility.
However, in accordance with the above prior art, the following problems are still remained to be solved.
That is, the radioactive waste treating (solidification) facility must be cleaned up after completing a designated treatment. At that time, the portions touched with the radioactive water are contaminated with radioactive material, and washed water of the portions become secondary radioactive waste and another treating facility for the secondary radioactive waste becomes necessary. Accordingly, in the radioactive waste treating (solidification) facility, it is preferable that the portions touched with radioactive waste must be reduced as small as possible.
Generally, in case of out-drum type kneader is used in the kneading solidification, both the kneading blade and the kneading vessel are contaminated with radioactive material, and both of them must be washed. On the contrary, in case of in-drum type kneader is used, only the kneading blade is contaminated. Therefore, only the kneading blade must be washed, and the amount of secondary radioactive material can be reduced.
In accordance with the prior art, the out-drum mixer type kneader is used, in order to make it possible to perform injecting solidification and kneading solidification together by a single facility. Accordingly, both the kneading blade and the kneading vessel are contaminated with radioactive material in the kneading solidification operation, and both of them must be washed. Therefore, the amount of the secondary radioactive waste can be hardly reduced.